Employee Stock and Benefit Plans (Employee Stock Purchase Plan Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount from market price percentage from ofering date	85.00%
Shares purchased under ESPP	79,200	49,700	53,600
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value, options exercised	$ 0	$ 0	$ 0

Discount rate from fair value on offering date that participants pay for shares.

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-Topic 718
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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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